pluginSetting: Fix calling of change function
pluginSetting: Fix calling of change function

A function itself is passed to this - not a pointer to a public plugin
function.

Fixes e.g. the bug that the `Preselect` setting in `morph` didn't
trigger when you clicked on it.

fbaumgardt/arethusa,fbaumgardt/arethusa,fbaumgardt/arethusa,alpheios-project/arethusa,PonteIneptique/arethusa,alpheios-project/arethusa,Masoumeh/arethusa,alpheios-project/arethusa,Masoumeh/arethusa,latin-language-toolkit/arethusa,PonteIneptique/arethusa,latin-language-toolkit/arethusa